Method for installing an external line on a deployed drilling riser

ABSTRACT

A method for assembling a marine drilling riser includes assembling a predetermined number of sections of the marine drilling riser and extending them into a body of water from a drilling platform. The assembling including affixing a selected number of external line guides to the riser at selected longitudinal positions. The line guides are initially closed to be substantially at most equal a diameter of buoyancy devices on the riser. The line guides are subsequently opened to extend beyond the buoyancy device diameter. A predetermined length of fluid external line is moved to adjacent the assembled riser and the fluid conduit is coupled to the external line guides. The external line guides are locked and assembly of the riser is completed and tension is applied thereto.

BACKGROUND

This disclosure is related to the field of subsea drilling. Moreparticularly, the disclosure relates to methods for installing anexternal fluid line on a deployed marine drilling riser.

The present disclosure is described in terms of attaching a mud returnline (MRL) pipe to an at least partially deployed marine drilling riserfor use in subsea mudlift pump (SMP) marine drilling operations. Itshould be clearly understood that the scope of the present disclosure isnot limited to such SMP applications, but extends to all possible usesfor an additional external line used with a marine drilling riser. Suchlines may include, without limitation, both fluid carrying lines(conduits or pipes) and electrical and/or optical cables.

Marine drilling risers known in the art comprise a relatively largediameter conduit that couples to a wellhead disposed proximate thebottom of a body of water. The large diameter conduit extends from thewellhead and extends to a drilling platform on the water surface. Thedrilling platform may be floating or bottom supported. The largediameter conduit provides a path closed to the seawater external theretofor passage of drilling tools used to drill a wellbore below thewellhead in the formations below the water bottom and may provide atleast part of a fluid return path to the drilling platform for drillingfluid being discharged from the wellbore. The large diameter conduit mayinclude a plurality of smaller diameter fluid lines disposed externallythereto. The smaller diameter fluid lines may be used for purposes,including but not limited to choke and kill functions and providinghydraulic fluid pressure to operate devices on the wellhead. The smallerdiameter fluid lines are typically affixed to the larger diameterconduit by attachment rings coupled to the exterior of the largediameter conduit and/or through openings in flanges that are affixed tothe longitudinal ends of each segment (“joint”) of the larger diameterconduit to assemble them end to end to form the completed marine riser.Marine risers known in the art also typically include buoyancy devicesaffixed to an exterior of the large diameter conduit to support theweight of the riser so that the riser will not collapse under its ownweight when deployed.

International Patent Application Publication No. WO 2013/024354discloses a subsea mudlift pump (SMP) module that may be attached to amarine drilling riser. The SMP module may be attached to the riser usinga modified riser joint (MRJ) coupled within the riser, wherein the MRJincludes docking and hydraulic couplings to secure the SMP module to theMRJ. If necessary, the SMP module may be detached from the riser (at theMRJ) during wellbore construction operations without the need to(“recover”) disassemble the riser, wherein the marine drilling riserextends from a wellhead proximate the water bottom to a drillingplatform on the water surface. The MRJ includes at least one hydraulicconnection to the interior of the marine drilling riser. The hydraulicconnection is coupled to an inlet of at least one pump on the SMPmodule. An outlet of the at least one pump on the SMP module may becoupled to a mud return line (MRL), wherein drilling mud that is pumpedfrom the interior of the riser is lifted to the drilling platform on thewater surface. The at least one pump on the SMP module may be controlledto maintain a selected fluid pressure at any selected depth in themarine drilling riser and/or in a wellbore drilled through formationsbelow the water bottom.

In assembling a marine drilling riser using an SMP module as describedin the above cited publication, it is desirable to provide a separatemud return line from the outlet of the at least one pump to the surface.There are other applications in which marine riser is used in which anadditional external, rigid fluid line or an external line such as anumbilical cable may be desirable to be used after the riser is deployed.Known structures for marine drilling risers make such post-deploymentattachment of an additional external line impractical.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example SMP module.

FIG. 2 shows an example mud return line (MRL) clamp.

FIG. 3 shows an example bottom end MRL clamp.

FIG. 4 shows a plan view of a drilling deck on a drilling platformindicating relative positions of the well center and a make up hole forthe MRL.

FIG. 5 shows a side view of the drilling platform wherein the MRL isbeing assembled in the make up hole.

FIG. 6 shows the example MRL clamp of FIG. 2 in the deployment position.

FIG. 7 shows the bottom end MRL clamp in the deployment position.

FIG. 7A shows details of a lower external end connector in side view forclarification of an internal flow conduit.

FIG. 8 shows the SMP module affixed to the riser as it is being loweredinto the water during riser assembly.

FIG. 9 shows the MRL being moved to adjacent the riser and being coupledto the riser using the MRL clamps.

FIG. 10 shows final assembly of a gooseneck and API specification mudreturn hose to an upper end of the MRL to complete the assembly of theMRL to the SMP module and the riser.

FIGS. 11A-11C show an example guide wire anchor and various releasemechanisms therefore.

DETAILED DESCRIPTION

FIG. 1 shows one example of a subsea mudlift pump (SMP) module 40 thatmay be used with a marine drilling system wherein a marine drillingriser (hereinafter simply “riser”) extends between a wellhead (notshown) deployed on the water bottom and a drilling platform (FIG. 5) onthe water surface. The SMP module 40 may be assembled to the riser 12below the drilling platform, either in the body of water or in the “moonpool” of a floating drilling platform to a specific riser segment thathas features for mating the SMP module 40 both hydraulically andmechanically thereto. An example of such riser segment, called amodified riser joint (MRJ, shown at 13 in FIG. 8) and the mechanical andhydraulic connections between it and the SMP module 40 are describedmore fully in International Patent Application Publication No. WO2013/024354 as set forth in the Background section herein. The SMPmodule 40 may have one or more (three shown in FIG. 1) pumps 42 that arein fluid communication on an inlet side thereof with a fluid outletdisposed in or forming part of the MRJ (13 in FIG. 8). An outlet of thepumps 42, as explained more fully below, may lift fluid from within theriser through a mud return line (MRL, shown at 24 in FIG. 5) to thedrilling unit.

The pumps 42 may be mounted on a platform, frame or plate structure 41that may include a semi-circular opening on one side to enableengagement with a mating feature (not shown) on the MRJ. Features suchas an externally mounted ring (not shown) may be provided on the MRJ tohold the structure 41 in a selected axial position along the MRJ. Apossible advantage of the configuration of the pump module 40 shown inFIG. 1 is that its weight may be more evenly circumferentiallydistributed around the riser 12 thus reducing lateral stresses on theriser 12. The foregoing example SMP module 40 is shown in and describedwith reference to FIGS. 2 and 3 in the above cited InternationalApplication Publication. Another example structure for a SMP module isdescribed with reference to FIGS. 4 and 5 in the same Publication.

FIG. 2 shows an example external line guide 11, which in the presentexample includes a clamp 10, a line retainer 14 pivotally coupled to theclamp 10 and a line retaining line clamp 16, which may be opened andclosed, e.g., by a remotely operated vehicle (ROV) or during movement ofthe riser below a drilling deck (FIG. 5) of a drilling platform. Thepipe retainer 14 is shown in its folded/secured position. The externalpipe guide 11 may be clamped to the riser 12 during a riser assemblyprocedure in the folded position shown in FIG. 2, for example, one toeach riser joint. In applications such as subsea mudlift drilling wherea riser mounted SMP module is used, such external line guides may becoupled to the riser joints above the position of the SMP module (40 inFIG. 1) on the riser (12 in FIG. 8). As used in the present context, theterm “line” may mean any longitudinally extensive element thattransports a medium, energy or signals, including, without limitation,fluid carrying conduits or pipes, electrical cable and optical cablesuch as armored cable (e.g., umbilical cables).

In the folded or closed position, the external line guides 11 may fitentirely inside a (e.g., 55 inch) buoyancy device (“can”) outerdiameter, shown in outline at 18. The external line guides 11 may beclamped to the riser 12 at any suitable location above or below buoyancycans (not shown separately) affixed to respective riser joints. Theexternal line guide 11 may be affixed to the riser 12 in thefolded/secured position for running on the riser through a well centeropening on the drilling deck of the drilling platform (see FIGS. 4 and5) as the riser is assembled and run to a wellhead (not shown) on thewater bottom.

FIG. 3 shows a lower external line end connector 11A. A split clamp 10Amay be clamped on the riser (12 in FIG. 8) in the folded/securedposition as shown in FIG. 3. When so deployed the lower external lineend connector 11A may also fit entirely inside buoyancy can outerdiameter 18 and may therefore be affixed to the riser (12 in FIG. 8)while assembling and running the riser through the main well centeropening (see FIG. 4). The lower external line end connector 11A mayinclude a clamp 10A similar in structure to the clamp shown at 10 inFIG. 2 for affixing the lower end connector 11A to the riser, a pivotingarm 14A and a remotely operated vehicle (ROV) operated locking mechanism16A. In some embodiments, an outlet pipe from SMP module (40 in FIG. 1)may have a six inch internal diameter, and a MRL pipe, to be explainedfurther below, may have a similar internal diameter. In someembodiments, a swivel and connector may have 100 bar working pressurerating based on pre-qualified riser pin-box connector design principles.

FIG. 4 shows a plan view of the drill floor 21 of the drilling platform.A main well center 20 is where well construction devices are movedthrough the drill floor 21. Such devices in the present example mayinclude the riser as it is assembled and extended into the water belowthe drilling platform to the wellhead (not shown) on the water bottom.An auxiliary well center 22 may include devices (FIG. 5) for assemblingand holding predetermined lengths of drilling tools, conduit and otherdevices for eventual movement and placement over the main well center20.

FIG. 5 shows a side view of the drilling platform, including an upperdeck 28, where an opening for the main drill center (20 in FIG. 4) isdisposed, and a lower deck 26 disposed below the upper deck 28. Thelower deck 26 may include a pipe cart or subsea tree carrier 22A forholding assembled lengths of drilling tools, for example tubular items,for example, riser, MRL, drill pipe, drilling tools, casing, or anumbilical cable, etc. The pipe cart or subsea tree carrier 22A may beused to assemble such lengths of tubular items. . In the presentexample, an external line to be affixed to the riser after at leastpartial deployment thereof may include a MRL 24. The pipe cart or subseatree carrier 22A may hold an assembled length thereof for lateralmovement toward the main drill center (20 in FIG. 4). The pipe cart orsubsea tree carrier 22A may make such movement by being transportedalong rails 27 on the lower deck 26.

In the present example method, an external pipe to be secured in theexternal line guides (11 in FIG. 2) and the lower external lineconnector (11A in FIG. 3) may be a mud return line (MRL) pipe. Aselected length, for example 300 meters, of the MRL pipe 24 may beassembled over the auxiliary well center (22 in FIG. 4) and hung off inthe pipe cart or subsea tree carrier 22A. The MRL pipe 24 may be madefrom substantially rigid conduit segments such as may be made from steelor alloys known in the art for use in conducting fluid under pressure,and connected end to end by, e.g., threaded connections at thelongitudinal ends of each conduit segment or by flange couplings. Itwill be appreciated that threaded connections may reduce the requiredlateral space for the MRL pipe 24 and enable affixing the MRL pipe 24closer to the exterior of the riser 12. A guide wire 23 may be deployedthrough the MRL pipe 24. A standard type ROV operated guide wire anchor(See 60 in FIG. 11A) may be disposed at a lower end of the guide wire23. In other embodiments, the MRL pipe 24 may be assembled over orproximate the main well center (20 in FIG. 4). MRL pipe assembly maytake place prior to, contemporaneously with or after assembly andrunning of the riser, one example of which will be described furtherbelow.

The riser 12 may be assembled over the main drill center (20 in FIG. 4)and extended toward the subsea wellhead (not shown) in accordance withmarine drilling riser deployment techniques known in the art. In thepresent example embodiment, where a SMP module is to be used, at aselected position along the riser 12, the MRJ (13 in FIG. 8) and the SMPmodule (40 in FIG. 1) may be coupled to the riser 12. It is within thescope of the present disclosure that the SMP module (40 in FIG. 1) willbe affixed to the MRJ (13 in FIG. 8) with the riser 12 suspended suchthat the SMP module (40 in FIG. 1) may be moved along the rails 27 onthe lower deck 26 to enable affixing to the drilling riser 12. After theSMP module (40 in FIG. 1) is affixed to the MRJ (13 in FIG. 8), assemblyof the riser 12 may continue according to riser assembly and runningprocedures known in the art. In other embodiments, the SMP module (40 inFIG. 1) may be affixed to the MRJ (13 in FIG. 8) after the riser 12 issubstantially completely assembled and is extended to proximate (e.g.,within 25 meters) of the wellhead (not shown) on the water bottom.

Referring to FIG. 6, as the riser 12 is assembled, one or more externalline guides 11 may be coupled to each riser segment (“joint”) andsubsequently opened. Opening may be performed, for example, above thewater line and below the upper deck (28 in FIG. 5) in the moon pool ofthe drilling platform as will be explained below with reference to FIG.7, or may be performed in the water by a ROV. In the present embodiment,such attachment of the external line guides (11 in FIG. 6) may be to theriser joints above the MRJ (13 in FIG. 8), but the scope of the presentdisclosure is not so limited. When the external line guides 11 aresubsequently opened to the position shown in FIG. 6 either by a suitabledevice disposed below the upper deck (28 in FIG. 5) or after the riseris substantially completely assembled, e.g., such as by using an ROV(not shown), the line retaining line clamp 16 will be positioned outsidethe external diameter of the buoyancy cans, shown in outline at 18.

In the present example, and referring to FIG. 7, the external line endconnector 11A may be moved to the deployment position (open) in the moonpool by the use of a “cherry picker” or utility transporter on the upperdeck (28 in FIG. 5) after the SMP module (40 in FIG. 8) is docked on theMRJ (13 in FIG. 8). In another embodiment, the external line endconnector 11A may be moved to the open position shown in FIG. 7 in thewater, for example, using an ROV. FIG. 7A shows details of the lower endconnector 11A in side view for clarification of an internal flowconduit. The internal flow conduit is shown at 16A and may be coupledhydraulically to the MRL pipe (24 in FIG. 8) when the riser is fullyassembled and tensioned.

Referring to FIG. 8, the SMP module 40 may be observed coupled to theriser 12 on the MRJ 13. A mud outlet conduit 43 may extend from adischarge of the at least one pump on the SMP module 40 to the lowerexternal line end connector 11A affixed to the MRJ 13. Assembly of theriser 12 may then continue, as previously explained, until the bottom ofthe riser 12 is deployed to a selected distance, for example,approximately 25 meters (80 ft) above the subsea wellhead. At such time,an ROV may be operated to connect the guide wire anchor (60A in FIG.11A) to an anchor base (60B in FIG. 11A) on the lower external line endconnector 11A on the MRJ 13.

Referring to FIG. 9, the pipe cart or subsea tree carrier 22A may thenmove the previously assembled MRL pipe 24 into a position adjacent tothe riser 12 (i.e., in each of the MRL line guides (11 in FIG. 6) whilethe guide wire 23 is tensioned.

At this time, the lower end of MRL pipe 24 may be located about 3 metersabove a lower external line end connector (16A in FIG. 7A). In thepresent example embodiment, the ROV may then be used to move the MRLpipe 24 into each retaining line clamp and to close the retaining lineclamp (16 in FIG. 6) on each of the external line guides (11 in FIG.6)Thus, the MRL pipe 24 is locked to the exterior of the riser 12, butmay be moved to some extent longitudinally with respect to the riser 12.The guide wire 23 may be removed from the MRL pipe 24 by releasing theguide wire anchor (60A in FIG. 11A) from the anchor base (60B in FIG.11A) Releasing the guide wire anchor may be performed, for example byusing the ROV to lift a release collar (60C in FIG. 11B) or by applyingsufficient tension on the guide wire 23 to break a shear pin in a lowerrelease collar (60D in FIG. 11C), either of which will retract anchortabs (60E in FIG. 11A) that otherwise retain the anchor in the anchorbase.

The riser 12 may then be lifted to dock the MRL pipe 24 in the lowerexternal line end connector (11A in FIG. 7) while the ROV makes anoptical survey for observation by the system operator. The ROV may fixthe MRL pipe 24 by closing the line clamp 16A on the lower external endconnector (11A in FIG. 7) The MRL pipe 24 may then be removed from thepipe cart or subsea tree carrier 22A, for example, by tensioning theupper end of the MRL pipe 24 toward the riser and removing retainingslips. The riser 12 may then be lowered and hung off using tensioningdevices known in the art. Referring to FIG. 10, an upper guide andgooseneck 46 with an American Petroleum Institute (API) qualified hosestorm loop 48 may be coupled to the upper end of the MRL pipe 24. Ahang-off bracket and tensioner chain/wire with a turnbuckle may beassembled to a lug on the gooseneck 46.

The riser 12 may then then be lowered to the wellhead and lockedthereto, for example, using the ROV. The riser may then be tensioned toa pre-defined tension value by lifting on a riser tensioning ring (notshown) of any type known in the art. A gas handler and telescopic riserjoint may be deployed and hung off in the riser tensioner ring tocomplete assembly of the riser 12. In the present example, the gooseneck46 may be suspended at a depth of about 15 meters in the water uponfinal assembly of the riser 12.

During operation of the present example embodiment, fluid may bewithdrawn from the interior of the riser 12 through the MRJ 13 into anintake port of the at least one pump on the SMP module 40. Dischargefrom the at least one pump may then be directed through the MRL pipe 24,the API hose storm loop 48 and back to drilling fluid processingequipment (not shown) on the drilling platform.

Disassembly of the riser and MRL pipe may be performed by reversing theabove described procedure.

If the external line is, for example an umbilical cable, the pipe cartor subsea handling system may be substituted by a winch. The winch maybe used to extend a selected length of umbilical cable for eventualcoupling to the line guides as explained above with reference to the MRLpipe. The winch may be fixed position or may move laterally, e.g., alongthe rail on the lower deck of the drilling platform.

A riser and external line assembly method according to the presentdisclosure may enable relatively rapid assembly of an additionalexternal rigid fluid line to a deployed riser, e.g., for use with adocked subsea mudlift pump and associated mud return line. The lineguides and lower external line end connector are retractable and do notinfluence deployment of the riser significantly as the line guides canpass through the drill floor main well center opening unrestricted whenin the folded position. Deploying and attaching the additional externalline, such as a MRL pipe, after the riser has been deployed may haveseveral advantages. First, existing types of marine riser would not needsignificant modification, which may have high cost and long constructiontime. Second, such procedure may allow a mudlift system to have widerapplication as only one special joint of riser is needed as opposed tomodifying many joints with an extra return line. Any impact on health,safety and the environment may be reduced because the line guides may beaffixed to the riser above the drilling deck and/or prior to mobilizingthe riser from land shore base to the rig, and not over open water inthe moon pool. Such operation may reduce the risks for operators workingin the crowded moonpool or from falling while working with heavy objectsover open water, or from dropping line guides into the water. The numberof ROV operations may be reduced, again because the line guides may beaffixed to the riser before each riser joint is lowered into the water.Reducing the number of ROV operations may assist in reducing operatingtime and expense when running or retrieving the drilling riser. Finally,because most of the mud return line or other external line may be madefrom rigid conduit material and is fixed in place with respect to theriser, it may be less susceptible to damage than other forms of mudreturn line used in connection with subsea mudlift drilling known in theart. Methods according to the present disclosure may provide similarbenefits when used to assemble other types of external line to apartially or substantially fully deployed marine riser.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. A method for assembling a marine drilling riser,comprising: assembling a predetermined number of sections of the marinedrilling riser and extending the assembled sections into a body of waterfrom a drilling platform, the assembling including affixing a selectednumber of external line guides to the riser at selected longitudinalpositions along the riser, the external line guides initially in afolded position traversing a dimension at most substantially equal to adiameter of buoyancy devices affixable to the riser; moving the externalline guides to an open position such that a line clamp on each lineguide extends beyond the diameter of the buoyancy devices; moving apredetermined length of external line to adjacent the assembled riserand coupling the external to a line clamp on each of the external lineguides; closing the line clamp on each of the external line guides; andcompleting assembly of the riser and applying tension thereto.
 2. Themethod of claim 1 wherein the external line comprises a mud return linein fluid communication at one end to an outlet of a subsea mudlift pump.3. The method of claim 2 wherein the one end of the mud return line iscoupled to a connector affixed to an exterior of the riser proximate thesubsea mudlift pump, and wherein the subsea mudlift pump is coupled toan exterior of the riser on a modified riser joint.
 4. The method ofclaim 2 wherein the coupling the mud return line to the connectorcomprises lifting the riser to engage the mud return line with theconnector.
 5. The method of claim 1 wherein the assembling thepredetermined length of external line is performed at a selected lateraldistance from a main well center on the drilling platform.
 6. The methodof claim 5 wherein the moving the predetermined length of external linecomprises moving a pipe cart or subsea tree carrier laterally toward thepredetermined number of sections of riser.
 7. The method of claim 1wherein the external line guides are affixed to the riser in a closedposition such that the external line guides extend laterally from theriser at most to an outer diameter defined by buoyancy cans.
 8. Themethod of claim 7 wherein the external line guides are operated to anopen position after being lowered through a drilling deck on thedrilling platform, the open position extending a pipe retaining lineclamp on each external line guide to beyond the outer diameter definedby the buoyancy cans.
 9. The method of claim 8 wherein the operating theexternal line guides is performed either above a water surface in a moonpool of the drilling platform or below a water surface by a remotelyoperated vehicle.